The earliest armed peacekeeping operation was the First UN Emergency Force (UNEF I) deployed successfully in 1956 to address the Suez Crisis.

The UN Operation in the Congo (ONUC), launched in 1960, was the first large-scale mission having nearly 20,000 military personnel at its peak. ONUC demonstrated the risks involved in trying to bring stability to war-torn regions - 250 UN personnel died while serving on that mission, including the Secretary-General Dag Hammarskjold.

In 1988, UN peacekeepers were awarded the Nobel Peace Prize. At that time, the Nobel Committee cited “the Peacekeeping Forces through their efforts have made important contributions towards the realization of one of the fundamental tenets of the United Nations. Thus, the world organization has come to play a more central part in world affairs and has been invested with increasing trust”.